60 research outputs found
Arbitration, Mediation and Cheap Talk
Consider an agent (manager,artist, etc.) who has imperfect private information about his productivity. At the beginning of his career (period 1, “short run”), the agent chooses among publicly observable actions that generate imperfect signals of his productivity. The actions can be ranked according to the informativeness of the signals they generate. The market observes the agent’s action and the signal generated by it, and pays a wage equal to his expected productivity. In period 2 (the “long run”), the agent chooses between a constant payoff and a wage proportional to his true productivity, and the game ends. We show that in any equilibrium where not all types of the agent choose the same action, the average productivity of an agent choosing a less informative action is greater. However, the types choosing that action are not uniformly higher. In particular, we derive conditions for the existence of a tripartite equilibrium where low and high types pool on a less informative action while medium (on average, lower) types choose to send a more informative signal.signalling, career concerns
A countermeasure against bright-light attack on superconducting nanowire single-photon detector in quantum key distribution
We present an active anti-latching system for superconducting nanowire
single-photon detectors. We experimentally test it against a bright-light
attack, previously used to compromise security of quantum key distribution.
Although our system detects continuous blinding, the detector is shown to be
partially blindable and controllable by specially tailored sequences of bright
pulses. Improvements to the countermeasure are suggested.Comment: 10 pages, 6 figure
Photon-number-resolution with sub-30-ps timing using multi-element superconducting nanowire single photon detectors
A photon-number-resolving detector based on a four-element superconducting
nanowire single photon detector is demonstrated to have sub-30-ps resolution in
measuring the arrival time of individual photons. This detector can be used to
characterize the photon statistics of non-pulsed light sources and to mitigate
dead-time effects in high-speed photon counting applications. Furthermore, a
25% system detection efficiency at 1550 nm was demonstrated, making the
detector useful for both low-flux source characterization and high-speed
photon-counting and quantum communication applications. The design, fabrication
and testing of this detector are described, and a comparison between the
measured and theoretical performance is presented.Comment: 13 pages, 5 figure
Tunnel field-effect transistors for sensitive terahertz detection
The rectification of electromagnetic waves to direct currents is a crucial
process for energy harvesting, beyond-5G wireless communications, ultra-fast
science, and observational astronomy. As the radiation frequency is raised to
the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics
becomes challenging and requires alternative rectification protocols. Here we
address this challenge by tunnel field-effect transistors made of bilayer
graphene (BLG). Taking advantage of BLG's electrically tunable band structure,
we create a lateral tunnel junction and couple it to an antenna exposed to THz
radiation. The incoming radiation is then down-converted by the tunnel junction
nonlinearity, resulting in high-responsivity (> 4 kV/W) and low-noise (0.2
pW/}) detection. We demonstrate how switching from
intraband Ohmic to interband tunneling regime can raise detectors' responsivity
by few orders of magnitude, in agreement with the developed theory. Our work
demonstrates a potential application of tunnel transistors for THz detection
and reveals BLG as a promising platform therefor
Electron energy relaxation in disordered superconducting NbN films
We report onthe energy relaxation of electrons studied by means of magnetoconductance and photoresponse in a series of superconducting NbN film with thickness in the range from 3 to 33 nm. The inelastic scattering rate of electrons on phonons obeys Tntemperature dependence where the exponent is in the range ????≈3.2÷3.8and shows no systematically dependence on the degree of disorder. At 11K electron-phonon scattering times are in the range11.9 -17.5 ps.We show that in the studied NbN films the Debye temperature and the densityof phononstatesare both reduced with respect to bulk material. In the thinnest studied films reduced density of states along with the phonon trapping slowsdown the energy relaxationofelectrons by afactor of 4 as compared to the prediction of the tree dimensional phonon mode
Electron energy relaxation in disordered superconducting NbN films
We report on the inelastic-scattering rate of electrons on phonons and
relaxation of electron energy studied by means of magnetoconductance, and
photoresponse, respectively, in a series of strongly disordered superconducting
NbN films. The studied films with thicknesses in the range from 3 to 33 nm are
characterized by different Ioffe-Regel parameters but an almost constant
product q_Tl(q_T is the wave vector of thermal phonons and l is the elastic
mean free path of electrons). In the temperature range 14-30 K, the
electron-phonon scattering rates obey temperature dependencies close to the
power law 1/\tau_{e-ph} \sim T^n with the exponents n = 3.2-3.8. We found that
in this temperature range \tau_{e-ph} and n of studied films vary weakly with
the thickness and square resistance. At 10 K electron-phonon scattering times
are in the range 11.9-17.5 ps. The data extracted from magnetoconductance
measurements were used to describe the experimental photoresponse with the
two-temperature model. For thick films, the photoresponse is reasonably well
described without fitting parameters, however, for thinner films, the fit
requires a smaller heat capacity of phonons. We attribute this finding to the
reduced density of phonon states in thin films at low temperatures. We also
show that the estimated Debye temperature in the studied NbN films is
noticeably smaller than in bulk material.Comment: 23 pages, 6 figure
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